1. Field of the Invention
The present invention pertains to devices and methods of compressing and loading stents into delivery tubes, such as catheters. More particularly, the present invention pertains to devices and methods that utilize vibrations or oscillations to reduce the friction required to forcibly insert radially compressed stents into delivery tubes. Using the present invention, a wider range of sizes and lengths of stents can be loaded into delivery tubes without being damaged during the process.
2. General Background
Several types of stents are commonly used to prevent blood vessels from collapsing. Such stents are typically radially compressed prior to insertion and are placed in delivery tubes that allow the stents to be passed through blood vessels during placement to minimize the evasiveness of the implantation procedures. Once properly positioned, the stents are forced out of the delivery tubes and radially expand to thereby maintain a fluid passageway through the blood vessels.
There are two primary types of stents. One type of stent is formed of traditional metal alloys and is radially expanded by inflating a balloon around which it was radially compressed. Once expanded, the balloon is deflated and withdrawn from the blood vessel. More recently, self-expanding stents have been used that utilize Shape Memory Alloys (SMA) to form stents that automatically expand when exposed to body temperature. An example of an SMA is nickel titanium alloy (typically referred to as nitinol). SMA stents are originally formed in their radially expanded state and must be radially compressed to be inserted into delivery tubes. When radially compressed, it can become difficult to load stents into delivery tubes without damaging the stents, due to the frictional forces resulting from the stents resiliency. Traditionally, radially compressed stents are either pulled or pushed into the delivery tubes. When frictional forces are high, the pushing or pulling forces can damage the stents.
To prevent damage to unique geometry and long stents during loading procedures, a so called “inchworm” technique is often used to load such stents into delivery tubes. Using that technique, rather than compressing the entire stent, small portions of the stent are reduced in diameter and are pushed into a delivery tube one portion at a time. This method requires skilled operators and normally greatly extends the loading time, thereby making it undesirable.
In view of the foregoing, prior art techniques of loading stents into delivery tubes have limitations and drawbacks.